Details emerge on $5.5b Vic toll road

Victorians have a better idea of what the Western Distributor toll road will cost, but funding arrangements and the exact route are not yet settled.

The $5.5 billion project, a joint venture between the Victorian government and toll road operator Transurban, will link the West Gate Freeway and CityLink and will include both a tunnel and a new bridge over the Maribyrnong River.

Under the latest business case for the road, the Victorian government will kick in $400 million and has agreed to extend Transurban's CityLink tolls for a decade to pay for the road.

The state government will also seek a $1.5 million contribution from the federal government.

"This is a road of national importance, and it could be that the Commonwealth may want to treat it like other roads of national importance and provide a much more substantial contribution than an allocation in something of the vicinity of a third," Treasurer Tim Pallas told reporters on Tuesday.

The road will remove 6000 trucks a day from the West Gate Freeway and will take many trucks off western suburbs roads as they head for the Port of Melbourne, the business case says.

Opposition roads spokesman Ryan Smith said the project had been announced with "little funding attached to it" and no immediate benefits.